This invention relates to a relay pilot regulator for operating a main regulator, and in particular, to a relay pilot regulator having a combined loading and unloading valve which share a common operating linkage.
In fluid pressure systems, such as gas distribution systems, it is desirable to utilize a pressure regulator system which receives gas at an inlet pressure and regulates the flow of gas to provide and maintain a desired adjusted outlet pressure despite variations in downstream demand.
A pertinent prior art regulator system is described in U.S. Pat. No. 2,624,980. That system comprises a main regulator section including a main valve which is adjusted between its opened and closed position by a main regulator diaphragm connected to the main valve through a mechanical linkage. The main regulator diaphragm is subjected to the outlet pressure on one of its sides, and the outlet pressure tends to move the main regulator diaphragm to close the main valve. The other side of the main regulator diaphragm is subjected to a loading pressure, which tends to move the main regulator diaphragm to open the main valve. The main valve is also spring biased, and it is a balance of the spring, loading pressure and outlet pressure which determines the position of the main valve. A relay pilot regulator of the prior art system controls the loading pressure applied to one side of the main regulator diaphragm. The relay pilot regulator also comprises a diaphragm, which is spring biased against the outlet pressure. The relay pilot diaphragm is mechanically linked, through a double toggle linkage, to two separate and distinct valves. One of the valves, when open, supplies inlet gas to the loaded side of the main regulator diaphragm, thus increasing the loading pressure. This occurs when the outlet pressure has fallen below the desired level, and the increase in the loading pressure causes the main valve to open more, thereby increasing the outlet pressure to the desired level. The second valve is opened when the outlet pressure is too great, and operates to vent the loading pressure and thus decrease it, causing the main valve to move towards its closed position and reduce the outlet pressure.
The foregoing structure, although providing a workable regulator system, nevertheless, has some disadvantages. The relay pilot regulator requires two separate valve structures and two separate passageways, one for supplying the loading pressure and the other for venting the loading pressure. The double toggle linkage connecting the two separate valves is relatively complex and requires careful manufacturing and adjustment to achieve operation as intended, and the response of the relay pilot regulator is slower than desired because of the complex structure. Slower response time of the relay pilot regulator results in cycling of the main regulator as it seeks a main valve position for providing outlet gas at the desired outlet pressure, and this is undesirable. The improvements which would be desirable over the prior art pilot regulator are more simplified structure and faster response time.
Other relay pilot operated fluid pressure regulator systems have also been used, and in general they have been even more complex, some even requiring two diaphragms in the relay pilot regulator.